/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.table.planner.plan.rules.logical;

import org.apache.calcite.plan.RelOptRule;
import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.plan.RelOptUtil;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Join;
import org.apache.calcite.rel.core.RelFactories;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.tools.RelBuilder;
import org.apache.calcite.tools.RelBuilderFactory;

/**
 * This rules is copied from Calcite's {@link org.apache.calcite.rel.rules.JoinPushExpressionsRule}.
 * Modification:
 * - Supports SEMI/ANTI join using {@link org.apache.flink.table.planner.plan.utils.FlinkRelOptUtil#pushDownJoinConditions}
 * - Only push down calls on non-time-indicator field.
 */

/**
 * Planner rule that pushes down expressions in "equal" join condition.
 *
 * <p>For example, given
 * "emp JOIN dept ON emp.deptno + 1 = dept.deptno", adds a project above
 * "emp" that computes the expression
 * "emp.deptno + 1". The resulting join condition is a simple combination
 * of AND, equals, and input fields, plus the remaining non-equal conditions.
 */
public class FlinkJoinPushExpressionsRule extends RelOptRule {

	public static final FlinkJoinPushExpressionsRule INSTANCE =
			new FlinkJoinPushExpressionsRule(Join.class, RelFactories.LOGICAL_BUILDER);

	/** Creates a JoinPushExpressionsRule. */
	public FlinkJoinPushExpressionsRule(Class<? extends Join> clazz,
			RelBuilderFactory relBuilderFactory) {
		super(operand(clazz, any()), relBuilderFactory, null);
	}

	@Deprecated // to be removed before 2.0
	public FlinkJoinPushExpressionsRule(Class<? extends Join> clazz,
			RelFactories.ProjectFactory projectFactory) {
		this(clazz, RelBuilder.proto(projectFactory));
	}

	@Override
	public void onMatch(RelOptRuleCall call) {
		Join join = call.rel(0);

		// Push expression in join condition into Project below Join.
		RelNode newJoin = RelOptUtil.pushDownJoinConditions(join, call.builder());

		// If the join is the same, we bail out
		if (newJoin instanceof Join) {
			final RexNode newCondition = ((Join) newJoin).getCondition();
			if (join.getCondition().equals(newCondition)) {
				return;
			}
		}

		call.transformTo(newJoin);
	}
}

// End FlinkJoinPushExpressionsRule.java
